debuginfo: Generate unique DW_AT_names for compilation units to work around OSX linker bug

src/librustc_trans/context.rs

@@ -375,7 +375,10 @@ impl<'a, 'tcx> LocalCrateContext<'a, 'tcx> {
 
             let dbg_cx = if shared.tcx.sess.opts.debuginfo != NoDebugInfo {
                 let dctx = debuginfo::CrateDebugContext::new(llmod);
-                debuginfo::metadata::compile_unit_metadata(shared, &dctx, shared.tcx.sess);
+                debuginfo::metadata::compile_unit_metadata(shared,
+                                                           codegen_unit.name(),
+                                                           &dctx,
+                                                           shared.tcx.sess);
                 Some(dctx)
             } else {
                 None

src/librustc_trans/debuginfo/metadata.rs

@@ -762,31 +762,38 @@ fn pointer_type_metadata<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
 }
 
 pub fn compile_unit_metadata(scc: &SharedCrateContext,
+                             codegen_unit_name: &str,
                              debug_context: &CrateDebugContext,
                              sess: &Session)
                              -> DIDescriptor {
-    let compile_unit_name = match sess.local_crate_source_file {
-        None => fallback_path(scc),
-        Some(ref path) => {
-            CString::new(&path[..]).unwrap()
-        }
+    let mut name_in_debuginfo = match sess.local_crate_source_file {
+        Some(ref path) => path.clone(),
+        None => scc.tcx().crate_name(LOCAL_CRATE).to_string(),
     };
 
-    debug!("compile_unit_metadata: {:?}", compile_unit_name);
+    // The OSX linker has an idiosyncrasy where it will ignore some debuginfo
+    // if multiple object files with the same DW_AT_name are linked together.
+    // As a workaround we generate unique names for each object file. Those do
+    // not correspond to an actual source file but that should be harmless.
+    if scc.sess().target.target.options.is_like_osx {
+        name_in_debuginfo.push_str("@");
+        name_in_debuginfo.push_str(codegen_unit_name);
+    }
+
+    debug!("compile_unit_metadata: {:?}", name_in_debuginfo);
     // FIXME(#41252) Remove "clang LLVM" if we can get GDB and LLVM to play nice.
     let producer = format!("clang LLVM (rustc version {})",
                            (option_env!("CFG_VERSION")).expect("CFG_VERSION"));
 
-    let compile_unit_name = compile_unit_name.as_ptr();
-
+    let name_in_debuginfo = CString::new(name_in_debuginfo).unwrap();
     let work_dir = CString::new(&sess.working_dir.0[..]).unwrap();
     let producer = CString::new(producer).unwrap();
     let flags = "\0";
     let split_name = "\0";
 
     unsafe {
         let file_metadata = llvm::LLVMRustDIBuilderCreateFile(
-            debug_context.builder, compile_unit_name, work_dir.as_ptr());
+            debug_context.builder, name_in_debuginfo.as_ptr(), work_dir.as_ptr());
 
         return llvm::LLVMRustDIBuilderCreateCompileUnit(
             debug_context.builder,
@@ -798,10 +805,6 @@ pub fn compile_unit_metadata(scc: &SharedCrateContext,
             0,
             split_name.as_ptr() as *const _)
     };
-
-    fn fallback_path(scc: &SharedCrateContext) -> CString {
-        CString::new(scc.tcx().crate_name(LOCAL_CRATE).to_string()).unwrap()
-    }
 }
 
 struct MetadataCreationResult {

src/test/debuginfo/multi-cgu.rs

@@ -0,0 +1,67 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+// This test case makes sure that we get proper break points for binaries
+// compiled with multiple codegen units. (see #39160)
+
+
+// min-lldb-version: 310
+
+// compile-flags:-g -Ccodegen-units=2
+
+// === GDB TESTS ===============================================================
+
+// gdb-command:run
+
+// gdb-command:print xxx
+// gdb-check:$1 = 12345
+// gdb-command:continue
+
+// gdb-command:print yyy
+// gdb-check:$2 = 67890
+// gdb-command:continue
+
+
+// === LLDB TESTS ==============================================================
+
+// lldb-command:run
+
+// lldb-command:print xxx
+// lldb-check:[...]$0 = 12345
+// lldb-command:continue
+
+// lldb-command:print yyy
+// lldb-check:[...]$1 = 67890
+// lldb-command:continue
+
+
+#![feature(omit_gdb_pretty_printer_section)]
+#![omit_gdb_pretty_printer_section]
+
+mod a {
+    pub fn foo(xxx: u32) {
+        super::_zzz(); // #break
+    }
+}
+
+mod b {
+    pub fn bar(yyy: u64) {
+        super::_zzz(); // #break
+    }
+}
+
+fn main() {
+    a::foo(12345);
+    b::bar(67890);
+}
+
+#[inline(never)]
+fn _zzz() {}